I'm an architecture student rendering in vray, generally through Rhino.
I consistenly have problems when printing the renders, the change in quality on paper to the screen is remarkable. I am rendering to the correct resoloution, with what I think is a good understanding of vray rendering settings.
One common probelm I keep getting is weird radial patterns eminating away from the object another object (such as an architectural model) sits on, and unrelaistic color reflections.
I generally save my files as a PNG, then print straight out of photoshop.